Heat treatable coated articles with metal nitride layer and methods of making same

ABSTRACT

A heat treatable coated article including a solar management layer for reflecting infrared (IR) or the like, is provided between a substrate and an overlying dielectric layer. An underlying dielectric layer between the substrate and solar management layer is optional. In certain embodiments, the solar management layer may include NiCrN x  while the dielectric layer(s) may include a nitride such as silicon nitride. By nitriding the solar management layer, it has been found that the resulting coated article is more color stable upon heat treatment (HT). For example, the coated article may have a ΔE* value (transmissive and/or glass side reflective) of no greater than 5.0, more preferably no greater than 4.0, and most preferably no greater than 3.0. Coated articles herein may be used in the context of insulating glass (IG) window units, vehicle windows, or the like.

This is a continuation of application Ser. No. 09/847,663, filed May 3,2001 now U.S. Pat. No. 6,524,714, the entire content of which is herebyincorporated by reference in this application.

This invention relates to coated articles that have approximately thesame color characteristics as viewed by the naked eye before and afterheat treatment (e.g., thermal tempering), and corresponding methods.Such coated articles may be used in insulating glass (IG) units, vehiclewindows, and/or other suitable applications.

BACKGROUND OF THE INVENTION

The need for color matchability of coated articles (before heattreatment vs. after heat treatment) is known. Glass substrates are oftenproduced in large quantities and cut to size in order to fulfill theneeds of a particular situation such as a new multi-window and dooroffice building, vehicle window needs, etc. It is often desirable insuch applications that some of the windows and/or doors be heat treated(i.e., tempered, heat strengthened or bent), while others need not be.Office buildings often employ IG units and/or laminates for safetyand/or thermal control. It is often desirable that the units and/orlaminates which are heat treated (HT) substantially match their non-heattreated counterparts (e.g., with regard to color, reflectance, and/orthe like) for architectural and/or aesthetic purposes.

U.S. Pat. No. 5,376,455 discloses a coated article including:glass/Si₃N₄/NiCr/Ag/NiCr/Si₃N₄. Unfortunately, the coating system of the'455 patent is not sufficiently color matchable after heat treatmentwith its non-heat-treated counterpart. In other words, the coatingsystem of the '455 patent has a rather high ΔE value. This means that,unfortunately, two different coated articles with different coatings(one to be heat treated, the other not to be) must be made for customerswho want their heat-treated and non-heat-treated coated articles toapproximately match colorwise as viewed by the naked eye.

As with the '455 patent, it has mostly been possible to achievematchability only by providing two different layer systems, one of whichis heat treated (HT) and the other is not. The necessity of developingand using two different layer systems to achieve matchability createsadditional manufacturing expense and inventory needs which areundesirable.

However, commonly owned U.S. Pat. No. 5,688,585 discloses a solarcontrol coated article including glass/Si₃N₄/NiCr/Si₃N₄, whereinmatchability is achieved with a single layer system. As explained atcolumn 9 of the '585 patent, it is a “requirement” of the '585 inventionthat the NiCr layer be substantially free of any nitride. An object ofthe '585 patent is to provide a sputter coated layer system that afterheat treatment is matchable colorwise with its non-heat-treatedcounterpart. However, the '585 patent uses a heat treatment (HT) of onlythree (3) minutes (col. 10, line 55). Longer heat treatments are oftendesired in order to attain better tempering or HT characteristics.Unfortunately, as explained below, it has been found that with longer HTtimes the coatings of the '585 patent cannot maintain low ΔE values andthus lose color matchability. In particular, it has surprisingly beenfound by the instant inventor that in coatings such as that of the '585patent, ΔE values jump significantly upward after HT for 4-5 minutes ata temperature of from about 600 to 800 degrees C.

Consider the following layer stack (see Example 7 below):glass/Si₃N₄/NiCr/Si₃N₄, where the underlayer of Si₃N₄ is about 50-70 Å(angstroms) thick, the NiCr layer is about 325 Å thick (the NiCr layeris not nitrided as deposited as can be seen in FIG. 15), and theovercoat of Si₃N₄ is about 210-310 Å thick. As explained in Example 7below, this coated article has a rather high transmissive ΔE* value ofabout 5.9 after a heat treatment (HT) at 625 degrees C. for ten (10)minutes. This high transmissive ΔE value means that a HT version of the'585 coated article does not approximately match colorwisenon-heat-treated counterpart versions with regard to transmissive colorafter 10 minutes of HT. This is not desirable.

The instant inventor believes that the high ΔE* value associated withthe coating of Example 7 herein is caused for at least the followingreasons. FIG. 15 is an XPS plot illustrating the Example 7 coatingbefore heat treatment (HT), while FIG. 16 illustrates the Example 7coating after HT. As shown in FIG. 15, before heat treatment the threedifferent layers are fairly separate and distinct. For example, prior toHT it can be seen that the Ni slopes 3 on either side of the NiCr layerare very steep, as are the Si and N slopes 5 and 7, respectively, on thelower side of the upper Si₃N₄ layer. Therefore, the vast majority of theNi is located in the NiCr layer and the vast majority of the Si and Nfrom the upper Si₃N₄ layer is located in that layer. However, FIG. 16illustrates that when the FIG. 15 coated article of Example 7 is heattreated (HT) for 10 minutes as discussed above, a significant portion ofthe Ni from the NiCr layer migrates into the upper Si₃N₄ layer.Additionally, upon HT a significant portion of the Si and N from theupper Si₃N₄ layer migrates into the NiCr layer. In other words, theinterface between the metal NiCr layer and the upper Si₃N₄ layer becomesblurred and non-distinct. This is evidenced in FIG. 16 by the less steepslope 3 a of the Ni on the upper/outer side of the NiCr layer, and bythe less steep slopes 5 a and 7 a of the Si and N on the lower side ofthe upper Si₃N₄ layer. Still further, it can be seen by comparing FIGS.15 and 16 that HT causes a significant amount of the Cr in the NiCrlayer to migrate within that layer toward the upper side thereof so thatit is not as uniformly distributed compared to pre-HT.

Unfortunately, the aforesaid migrations of the Si, N, Ni and Cr fromtheir FIG. 15 positions to their respective FIG. 16 positions due to HTcauses significant color shifting to occur and thus explains the largetransmissive ΔE* value associated with the coating of Ex. 7, and thuswith coatings of the '585 patent when exposed to lengthy heattreatments.

In view of the above, it will be apparent to those skilled in the artthat there exists a need for a coating or layer system that has a low ΔE(or ΔE*) value(s) (transmissive and/or glass side reflective) and thusgood color matchability characteristics after at least five (5) minutesof heat treatment (HT). It is a purpose of this invention to fulfill theabove-listed need, and/or other needs which will become more apparent tothe skilled artisan once given the following disclosure.

SUMMARY OF THE INVENTION

An object of this invention is to provide a coating or layer system thathas good color stability (i.e., a low ΔE* value(s)) with heat treatment(HT).

Another object of this invention is to provide a coating or layer systemhaving a ΔE* value (transmissive and/or glass side reflective) nogreater than 5.0 (more preferably no greater than 4.0, and mostpreferably no greater than 3.0) upon heat treatment (HT) at atemperature of at least about 600 degrees C. for a period of time of atleast 5 minutes (more preferably at least 7 minutes, and most preferablyat least 9 minutes).

Another object of this invention is to nitride a Ni and/or Cr inclusivelayer (e.g., a NiCr layer) to an extent so as to enable the resultingcoated article to have the aforesaid low ΔE value(s).

Another object of this invention is to fulfill one or more of theabove-listed objects.

Generally speaking, certain example embodiments of this inventionfulfill one or more of the above listed objects and/or needs byproviding a coated article comprising:

a layer system supported by a glass substrate, said layer systemcomprising a metal nitride inclusive layer located between first andsecond dielectric layers, wherein the second dielectric layer is atleast partially nitrided and positioned so that the metal nitrideinclusive layer is between the second dielectric layer and the glasssubstrate; and

wherein said coated article has a transmissive ΔE*_(T) value no greaterthan 5.0 after at least about 5 minutes of heat treatment at atemperature(s) of at least about 600 degrees C.

Certain other example embodiments of this invention fulfill one or moreof the above-listed objects and/or needs by providing a coated articlecomprising:

a layer system supported by a glass substrate, said layer systemcomprising a metal nitride inclusive layer located between said glasssubstrate and an at least partially nitrided dielectric layer, whereinthe metal nitride comprises at least one of NiN_(x) and CrN_(x) andcontacts said dielectric layer; and wherein said coated article has aglass side reflective ΔE*_(G) value no greater than 5.0 in view ofthermal tempering including heat treating for at least about 5 minutes.

Certain other example embodiments of this invention fulfill one or moreof the above-listed objects and/or needs by providing a coated articlecomprising:

a layer system supported by a class substrate, said layer systemcomprising a NiCrN_(x) inclusive layer wherein at least 50% of the Cr isnitrided, said NiCrN_(x) inclusive layer being located between andcontacting first and second dielectric layers, wherein the seconddielectric layer is at least partially nitrided and positioned so thatthe NiCrN_(x) inclusive layer is between the second dielectric layer andthe glass substrate; and wherein said coated article has a transmissiveΔE*_(T) value no greater than 5.0 following or due to heat treatment.

Still further example embodiments of this invention fulfill one or moreof the above-listed objects and/or needs by providing a method of makinga coated article, the method comprising:

providing a glass substrate;

depositing (e.g., via sputtering or any other suitable method/technique)a metal on the substrate in an atmosphere including a significant amountof nitrogen in order to form a metal nitride inclusive layer on theglass substrate;

depositing (e.g., via sputtering or any other suitable method/technique)a dielectric nitride inclusive layer on the substrate over the metalnitride inclusive layer; and

heat treating the article which includes at least the metal nitrideinclusive layer and the dielectric nitride inclusive layer for at least5 minutes, the metal nitride inclusive layer being nitrided to an extentso that after said heat treating the article has a ΔE value of nogreater than 5.0.

This invention will now be described with respect to certain embodimentsthereof as illustrated in the following drawings, wherein:

IN THE DRAWINGS

FIG. 1 is a partial side cross sectional view of an embodiment of acoated article (heat treated or not heat treated) according to anexample embodiment of this invention.

FIG. 2 is a partial cross-sectional view of an IG unit as contemplatedby this invention, in which the coating or layer system of FIG. 1 may beused.

FIG. 3 is an x-ray photoelectron spectroscopy (XPS) graph illustratingthe atomic % of components N, O, Na, Al, Si, Ca, Cr, and Ni throughoutthe thickness of a layer system according to Example 1 of this invention(before heat treatment), where the “depth” axis refers to the depth intothe coating and/or substrate from the exterior surface thereof ascompared to the depth into a conventional SiO₂ layer that would havebeen achieved over the same period of time (i.e., the Å depth is notactual depth, but instead is how deep into a reference SiO₂ layersputtering would have reached over the corresponding time).

FIG. 4 is an XPS graph illustrating the atomic % of components N, O, Na,Al, Si, Ca, Cr, and Ni throughout the thickness of the layer systemaccording to Example 1 of this invention after heat treatment at 625degrees C. for 10 minutes.

FIG. 5 is an x-ray photoelectron spectroscopy (XPS) graph illustratingthe atomic % of components N, O, Na, Al, Si, Ca, Cr, and Ni throughoutthe thickness of a layer system according to Example 2 of this invention(before heat treatment), where the “depth” axis refers to the depth intothe coating and/or substrate from the exterior surface thereof ascompared to the depth into a conventional SiO₂ layer that would havebeen achieved over the same period of time.

FIG. 6 is an XPS graph illustrating the atomic % of components N, O, Na,Al, Si, Ca, Cr, and Ni throughout the thickness of the layer systemaccording to Example 2 of this invention after heat treatment at 625degrees C. for 10 minutes.

FIG. 7 is an x-ray photoelectron spectroscopy (XPS) graph illustratingthe atomic % of components N, O, Na, Al, Si, Ca, Cr, and Ni throughoutthe thickness of a layer system according to Example 3 of this invention(before heat treatment), where the “depth” axis refers to the depth intothe coating and/or substrate from the exterior surface thereof ascompared to the depth into a conventional SiO₂ layer that would havebeen achieved over the same period of time.

FIG. 8 is an XPS graph illustrating the atomic % of components N, O, Na,Al, Si, Ca, Cr, and Ni throughout the thickness of the layer systemaccording to Example 3 of this invention after heat treatment at 625degrees C. for 10 minutes.

FIG. 9 is an x-ray photoelectron spectroscopy (XPS) graph illustratingthe atomic % of components N, O, Na, Al, Si, Ca, Cr, and Ni throughoutthe thickness of a layer system according to Example 4 of this invention(before heat treatment), where the “depth” axis refers to the depth intothe coating and/or substrate from the exterior surface thereof ascompared to the depth into a conventional SiO₂ layer that would havebeen achieved over the same period of time.

FIG. 10 is an XPS graph illustrating the atomic % of components N, O,Na, Al, Si, Ca, Cr, and Ni throughout the thickness of the layer systemaccording to Example 4 of this invention after heat treatment at 625degrees C. for 10 minutes.

FIG. 11 is an x-ray photoelectron spectroscopy (XPS) graph illustratingthe atomic % of components N, O, Na, Al, Si, Ca, Cr, and Ni throughoutthe thickness of a layer system according to Example 5 of this invention(before heat treatment), where the “depth” axis refers to the depth intothe coating and/or substrate from the exterior surface thereof ascompared to the depth into a conventional SiO₂ layer that would havebeen achieved over the same period of time.

FIG. 12 is an XPS graph illustrating the atomic % of components N, O,Na, Al, Si, Ca, Cr, and Ni throughout the thickness of the layer systemaccording to Example 5 of this invention after heat treatment at 625degrees C. for 10 minutes.

FIG. 13 is an x-ray photoelectron spectroscopy (XPS) graph illustratingthe atomic % of components N, O, Na, Al, Si, Ca, Cr, and Ni throughoutthe thickness of a layer system according to Example 6 of this invention(before heat treatment), where the “depth” axis refers to the depth intothe coating and/or substrate from the exterior surface thereof ascompared to the depth into a conventional SiO₂ layer that would havebeen achieved over the same period of time.

FIG. 14 is an XPS graph illustrating the atomic % of components N, O,Na, Al, Si, Ca, Cr, and Ni throughout the thickness of the layer systemaccording to Example 6 of this invention after heat treatment at 625degrees C. for 10 minutes.

FIG. 15 is an x-ray photoelectron spectroscopy (XPS) graph illustratingthe atomic % of components N, O, Na, Al, Si, Ca, Cr, and Ni throughoutthe thickness of a layer system according to Example 7 of this invention(before heat treatment), where the “depth” axis refers to the depth intothe coating and/or substrate from the exterior surface thereof ascompared to the depth into a conventional SiO₂ layer that would havebeen achieved over the same period of time.

FIG. 16 is an XPS graph illustrating the atomic % of components N, O,Na, Al, Si, Ca, Cr, and Ni throughout the thickness of the layer systemaccording to Example 7 of this invention after heat treatment at 625degrees C. for 10 minutes.

FIG. 17 is an x-ray photoelectron spectroscopy (XPS) graph illustratingthe atomic % of components N, O, Na, Al, Si, Ca, Cr, and Ni throughoutthe thickness of a layer system according to Example 8 of this invention(before heat treatment), where the “depth” axis refers to the depth intothe coating and/or substrate from the exterior surface thereof ascompared to the depth into a conventional SiO₂ layer that would havebeen achieved over the same period of time.

FIG. 18 is an XPS graph illustrating the atomic % of components N, O,Na, Al, Si, Ca, Cr, and Ni throughout the thickness of the layer systemaccording to Example 8 of this invention after heat treatment at 625degrees C. for 10 minutes.

FIG. 19 is an x-ray photoelectron spectroscopy (XPS) graph illustratingthe atomic % of components N, O, Na, Al, Si, Ca, Cr, and Ni throughoutthe thickness of a layer system according to Example 9 of this invention(before heat treatment), where the “depth” axis refers to the depth intothe coating and/or substrate from the exterior surface thereof ascompared to the depth into a conventional SiO₂ layer that would havebeen achieved over the same period of time.

FIG. 20 is an XPS graph illustrating the atomic % of components N, O,Na, Al, Si, Ca, Cr, and Ni throughout the thickness of the layer systemaccording to Example 9 of this invention after heat treatment at 625degrees C. for 10 minutes.

FIG. 21 is an x-ray photoelectron spectroscopy (XPS) graph illustratingthe atomic % of components N, O, Na, Al, Si, Ca, Cr, and Ni throughoutthe thickness of a layer system according to Example 10 of thisinvention (before heat treatment), where the “depth” axis refers to thedepth into the coating and/or substrate from the exterior surfacethereof as compared to the depth into a conventional SiO₂ layer thatwould have been achieved over the same period of time.

FIG. 22 is an XPS graph illustrating the atomic % of components N, O,Na, Al, Si, Ca, Cr, and Ni throughout the thickness of the layer systemaccording to Example 10 of this invention after heat treatment at 625degrees C. for 10 minutes.

DETAILED DESCRIPTION OF CERTAIN EXAMPLE EMBODIMENTS OF THE INVENTION

Certain embodiments of this invention provide a coating or layer systemthat may be used in applications such as IG units, vehicle windows,architectural windows, and/or other suitable applications. Certainembodiments of this invention provide a layer system that has excellentcolor stability (i.e., a low value of ΔE* and/or a low value of Δa*;where Δ is indicative of change in view of HT) with heat treatment(e.g., thermal tempering, bending, or thermal heat strengthening)monolithically and/or in the context of dual pane environments such asIG units or windshields. Such heat treatments often necessitate heatingthe coated substrate to temperatures from about 600° C. up to about 800°C. for at least about 5 minutes.

FIG. 1 is a side cross sectional view of a coated article according toan example embodiment of this invention. The coated article includessubstrate 11 (e.g., clear, green, bronze, grey, blue, or blue-greenglass substrate from about 1.0 to 12.0 mm thick), optional firstdielectric layer 13 (e.g., of or including silicon nitride (e.g.,Si₃N₄), titanium dioxide, titanium nitride, zirconium nitride, siliconoxynitride, or the like), IR reflecting nickel (Ni) or nickel-chromeinclusive layer 15 that is nitrided (e.g., NiCrN_(x)), and secondnitrided dielectric layer 17 (e.g., of or including silicon nitride(e.g., Si₃N₄), titanium nitride, zirconium nitride, silicon oxynitride,aluminum nitride, or the like). Thus, the coating system 19 includesmetal nitride layer 15 located between (directly or indirectly) a pairof dielectric anti-reflection layers 13 and 17. Underlayer 13 isoptional, and upper dielectric layer 17 is preferably at least partiallynitrided.

Surprisingly, it has been found that coatings according to thisinvention can be made more color stable with heat treatment (HT) iflayer 15 is nitrided during the deposition process (e.g., the layer isnitrided so as to be deposited as NiCrN_(x)). It is believed that by atleast partially nitriding layer 15 during the deposition process (i.e.,so that it is nitrided to some significant extent prior to HT),migration of N, Cr, and/or Ni can be reduced during HT thereby enablingthe resulting coated article to be more color-stable with HT (i.e., havea lower ΔE* value(s)). Metal in metal nitride layer 15 may or may not befully nitrided in different embodiments of this invention. For example,metal such as Cr in layer 15 may be at least about 40% nitrided incertain embodiments of this invention, more preferably at least about50% nitrided, even more preferably at least about 60% nitrided, and mostpreferably at least about 75% nitrided. When layer 15 is NiCrN_(x), itis believed that the layer includes at least Ni and CrN_(x). Inalternative embodiments of this invention, layer 15 may be an oxynitridelayer (e.g., a metal oxynitride). Thus, metal nitride layer 15 may ormay not include amounts of oxide in different embodiments of thisinvention.

In certain preferred embodiments of this invention, dielectricanti-reflection layers 13 and 17 each have an index of refraction lessthan that of metal nitride layer 15 for anti-reflective purposes (e.g.,silicon nitride layers 13 and 17 may have an index of refraction “n” offrom about 1.9 to 2.1, while the metal nitride layer 19 has an index “n”higher than that).

Other layer(s) below or above the illustrated coating system 19 may alsobe provided. Thus, while the layer system 19 is “on” or “supported by”substrate 11 (directly or indirectly), other layer(s) may be providedtherebetween. Thus, for example, the layer system 19 of FIG. 1 isconsidered “on” the substrate 11 even when other layer(s) are providedtherebetween.

In embodiments of this invention where layers 13 and 17 comprise siliconnitride (e.g., Si₃N₄), sputtering targets including Si employed to formthese layers may be admixed with up to 6-20% by weight aluminum orstainless steel (e.g. SS#316), with about this amount then appearing inthe layers so formed. Moreover, while layer 15 may be NiCrN_(x),NiN_(x), or CrN_(x) in certain embodiments of this invention, thesematerials are not limiting and other IR reflecting metal nitrides mayinstead be used. In NiCrN_(x) embodiments, any suitable ratio of Ni:Crmay be used. For example, the Ni:Cr ratio in this layer may be 50:50 incertain embodiments, may be 80:20 in other embodiments, and may be 90:10or any other suitable ratio in still other embodiments.

FIG. 2 illustrates the coating or layer system 19 of FIG. 1 beingutilized on surface #2 of an IG (insulating glass) window unit. In orderto differentiate the “inside” of the IG unit from its “outside”, the sun21 is schematically presented on the outside. The IG unit includesoutside glass pane or sheet 11 and inside glass pane or sheet 23. Thesetwo glass substrates (e.g., float glass 2 mm to 12 mm thick) are sealedat their peripheral edges by a conventional sealant (not shown) and areprovided with a conventional desiccant strip (not shown). The panes arethen retained in a conventional window or door retaining frame. Bysealing the peripheral edges of the glass sheets and replacing the airin insulating space (or chamber) 25 with a gas such as argon, a highinsulating value IG unit is formed. Optionally, insulating space 25 maybe at a pressure less than atmospheric pressure in certain alternativeembodiments, although this of course is not necessary in all IGembodiments. Coating 19 may be provided on the inner wall of substrate11 in certain embodiments of this invention (as in FIG. 2), and/or onthe inner wall of substrate 23 in other embodiments of this invention.

Turning back to FIG. 1, while various thicknesses may be used consistentwith one or more of the objects and/or needs discussed herein, accordingto certain exemplary embodiments of this invention, the preferredthicknesses and materials for the respective layers on the glasssubstrate 11 are as follows:

TABLE 1 (Thicknesses) Layer Preferred Range (Å) More Preferred (Å) Si₃N₄(layer 13) 30-250 Å 50-120 Å NiCrN_(x) (layer 15) 20-600 Å 50-350 ÅSi₃N₄ (layer 17) 100-500 Å  210-310 Å 

In certain exemplary embodiments, the color stability with lengthy HTdue at least to the nitriding of layer 15 results in substantialmatchability between heat-treated and non-heat treated versions of thecoating or layer system. In other words, in monolithic and/or IGapplications, in certain embodiments of this invention two glasssubstrates having the same coating system thereon (one HT afterdeposition and the other not HT) appear to the naked human eye to looksubstantially the same.

The values ΔE* and Δa* are important in determining whether or not thereis matchability, or substantial color matchability upon HT, in thecontext of this invention. Color herein is described by reference to theconventional a*, b* values. The term Δa* is simply indicative of howmuch color value a* changes due to HT.

The term ΔE* (and ΔE) is well understood in the art and is reported,along with various techniques for determining it, in ASTM 2244-93 aswell as being reported in Hunter et. al., The Measurement of Appearance,2^(nd) Ed. Cptr. 9, page 162 et seq. [John Wiley & Sons, 1987]. As usedin the art, ΔE* (and ΔE) is a way of adequately expressing the change(or lack thereof) in reflectance and/or transmittance (and thus colorappearance, as well) in an article after or due to HT. ΔE may becalculated by the “ab” technique, or by the Hunter technique (designatedby employing a subscript “H”). ΔE corresponds to the Hunter Lab L, a, bscale (or L_(h), a_(h), b_(h)). Similarly, ΔE* corresponds to the CIELAB Scale L*, a*, b*. Both are deemed useful, and equivalent for thepurposes of this invention. For example, as reported in Hunter et. al.referenced above, the rectangular coordinate/scale technique (CIE LAB1976) known as the L*, a*, b* scale may be used, wherein:

L* is (CIE 1976) lightness units

a* is (CIE 1976) red-green units

b* is (CIE 1976) yellow-blue units

and the distance ΔE* between L*_(o) a*_(o) b*_(o) and L*₁ a*₁ b*₁ is:

ΔE*=[(ΔL*)²+(Δa*)²+(Δb*)²]^(1/2)  (1)

where:

ΔL*=L* ₁ −L* _(o)  (2)

Δa*=a* ₁ −a* _(o)  (3)

Δb*=b* ₁ −b* _(o)  (4)

where the subscript “o” represents the coating (or coated article)before heat treatment and the subscript “1 ” represents the coating(coated article) after heat treatment; and the numbers employed (e.g.,a*, b*, L*) are those calculated by the aforesaid (CIE LAB 1976) L*, a*,b* coordinate technique. In a similar manner, ΔE may be calculated usingequation (1) by replacing a*, b*, L* with Hunter Lab values a_(h),b_(h), L_(h). Also within the scope of this invention and thequantification of ΔE* are the equivalent numbers if converted to thosecalculated by any other technique employing the same concept of ΔE* asdefined above.

In certain example non-limiting embodiments of this invention, coatingsor layer systems herein provided on clear monolithic glass substrateshave reflective color as follows before heat treatment, as viewed fromthe glass side of the coated article (R_(G) %):

TABLE 2a Glass Side Reflective Color (R_(G)) Before Heat TreatmentGeneral Preferred a* +2.0 to −8.0  0.0 to −2.5 b* −2.0 to +8.0  0.0 to+3.0 L* 10.0 to 75.0 20.0 to 70.3

Regarding transmissive color, in certain non-limiting embodiments ofthis invention, coatings or layer systems herein provided on clearmonolithic glass substrates have transmissive color as follows beforeheat treatment:

TABLE 2b Transmissive Color Before Heat Treatment General Preferred a* 0.0 to −5.0  0.0 to −2.0 b*  −2.0 to −15.0 −3.0 to −9.0 L* 10.0 to 70.020.0 to 50.0

After heat treatment (HT), in certain embodiments of this inventionlayer systems provided on clear monolithic glass substrates have colorcharacteristics ΔE*, and Δa*, and Δb* as follows, when viewed from theglass (G) side (as opposed to the layer side) of the coated article:

TABLE 3a Reflective Glass Side Color (ΔE*_(G), Δa*_(G) & Δb*_(G) AfterHeat Treatment General Preferred Most Preferred ΔE*_(G) is <= 5.0 <= 4.0<= 3.0 Δa*_(G) is <= 1.0 <= 0.6 <= 0.3 Δb*_(G) is <= 1.1 <= 0.7 <= 0.4

As for transmissive color characteristics, after HT in certainembodiments of this invention layer systems provided on clear monolithicglass substrates have transmissive color characteristics ΔE*, Δa* andΔb* as follows:

TABLE 3b Transmissive Color Characteristics (ΔE*_(T) & Δa*_(T)) After HTGeneral Preferred Most Preferred ΔE*_(T) is <= 5.0 <= 4.0 <= 3.0 Δa*_(T)is <= 1.3 <= 1.1 <= 0.8 Δb*_(T) is <= 6.0 <= 4.0 <= 3.0

Accordingly, as shown in Table 3 above, coated articles according tocertain embodiments of this invention have a ΔE*_(G) value (glass side)of no greater than 5.0, more preferably no greater than 4.0, and evenmore preferably no greater than 3.0; and have a Δa*_(G) value (glassside) of no greater than about 1.0, more preferably no greater than 0.6and most preferably no greater than 0.3. Also, in certain exampleembodiments and as shown in Table 3 above, coated articles according tocertain embodiments of this invention have a ΔE*_(T) value(transmissive) of no greater than 5.0, more preferably no greater than4.0, and even more preferably no greater than 3.0; and have a Δa*_(T)value (transmissive) of no greater than about 1.3, more preferably nogreater than 1.1, and most preferably no greater than 0.8. When one ormore of these are achieved, matchability may result.

EXAMPLES 1-10

The following ten Example coated articles (each ultimately annealed andheat treated) were made, with Examples 1-6 and 8-10 being made inaccordance with certain example embodiments of this invention andExample 7 being made for purposes of comparison where the NiCr layer wasnot nitrided. For Examples 1-6 and 8-10, the layer system on about 6.0mm thick clear soda-lime-silica glass substrate was: siliconnitride/NiCrN_(x)/silicon nitride (e.g., see FIG. 1). For comparativeExample 7, the layer system on about 6.0 mm thick clear soda-lime-silicaglass substrate was: silicon nitride/NiCr/silicon nitride (i.e., theNiCr layer was not nitrided in comparative Ex. 7). The coater/processsetups for the Examples were as follows.

For each example, a Leybold Terra-G six-chamber sputter coatingapparatus was used to sputter the coatings onto the glass substrates.Five cathodes were in each chamber, so there were a total of 30 cathodetargets in the sputter coater (not all were used). Cathode numberingutilizes the first digit to refer to the coater chamber, and the seconddigit to refer to the cathode position in that chamber. For example,cathode #42 was the second cathode (second digit) in the fourth (firstdigit) sputter chamber. Cathode #s 42, 55 and 61 were dual C-Mag typecathodes; and cathode #s 44 and 45 were planar cathodes. Below, “*”means Al content of approximately 10%. The line speed for Examples 5-10was 3.5 meters per minute (mi/min.), and was about 2.5 mi/min. forExamples 1-4. All gas flows in Table 4 (e.g., Ar and N) are presented inunits of sccm. Voltage is measured in terms of volts, and frequency interms of kHz. Pressure is measured in hPa, and power in kW. T-gas refersto trim gas used to individually adjust gas flows along cathode lengthto make corrections regarding layer thickness uniformity (all T-gas wasat 100 sccm). C % refers to the percentage (%) of trim gas introduced atthe center, while PS % refers to the percentage of the trim gasintroduced at the pump side, and VS % refers to the percentage of thetrim or tuning gas introduced at the viewer side. The NiCr targets wereapproximately 80/20 NiCr.

TABLE 4 Coater Setup/Processes for Examples Cathode Target Power VoltagePressure Ar N₂ Freq. T-Gas C % PS % VS % EXAMPLE #1 #42 Si/Al* 11.0 1922.11E−03 200 71.4 24.3 N 5% 45% 50% #44 Ni/Cr  38.46 411 3.15E−03 200115.4 DC Ar 80%  10% 10% #45 Ni/Cr  38.30 412 2.79E−03 200 114.9 DC Ar70%  20% 10% #55 Si/Al* 44.68 308 3.40E−03 200 268.1 27.1 N 5% 45% 50%#61 Si/Al* 44.72 299 3.98E−03 202 268.3 27.2 N 5% 45% 50% EXAMPLE #2 #42Si/Al* 11.0 192 2.11E−03 200 71.4 24.3 N 5% 45% 50% #44 Ni/Cr  38.46 4113.15E−03 200 153.8 DC Ar 80%  10% 10% #45 Ni/Cr  38.30 412 2.79E−03 200153.2 DC Ar 70%  20% 10% #55 Si/Al* 44.68 308 3.40E−03 200 268.1 27.1 N5% 45% 50% #61 Si/Al* 44.72 299 3.98E−03 202 268.3 27.2 N 5% 45% 50%EXAMPLE #3 #42 Si/Al* 11.0 192 2.11E−03 200 71.4 24.3 N 5% 45% 50% #44Ni/Cr  38.46 411 3.15E−03 200 192.3 DC Ar 80%  10% 10% #45 Ni/Cr  38.30412 2.79E−03 200 191.5 DC Ar 70%  20% 10% #55 Si/Al* 44.68 308 3.40E−03200 268.1 27.1 N 5% 45% 50% #61 Si/Al* 44.72 299 3.98E−03 202 268.3 27.2N 5% 45% 50% EXAMPLE #4 #42 Si/Al* 11.0 192 2.11E−03 200 71.4 24.3 N 5%45% 50% #44 Ni/Cr  38.46 411 3.15E−03 200 230.8 DC Ar 80%  10% 10% #45Ni/Cr  38.30 412 2.79E−03 200 229.8 DC Ar 70%  20% 10% #55 Si/Al* 44.68308 3.40E−03 200 268.1 27.1 N 5% 45% 50% #61 Si/Al* 44.72 299 3.98E−03202 268.3 27.2 N 5% 45% 50% EXAMPLE #5 #42 Si/Al* 11.0 192 2.11E−03 20071.4 24.3 N 5% 45% 50% #44 Ni/Cr  38.46 411 3.15E−03 200 51.9 DC Ar 80% 10% 10% #45 Ni/Cr  38.30 412 2.79E−03 200 51.7 DC Ar 70%  20% 10% #55Si/Al* 44.68 308 3.40E−03 200 268.1 27.1 N 5% 45% 50% #61 Si/Al* 44.72299 3.98E−03 202 268.3 7.2 N 5% 45% 50% EXAMPLE #6 #42 Si/Al* 11.0 1922.11E−03 200 71.4 24.3 N 5% 45% 50% #44 Ni/Cr  38.46 411 3.15E−03 20031.2 DC Ar 80%  10% 10% #45 Ni/Cr  38.30 412 2.79E−03 200 31.0 DC Ar70%  20% 10% #55 Si/Al* 44.68 308 3.40E−03 200 268.1 27.1 N 5% 45% 50%#61 Si/Al* 44.72 299 3.98E−03 202 268.3 27.2 N 5% 45% 50% EXAMPLE #7(Comparative Example) #42 Si/Al* 11.0 192 2.11E−03 200 71.4 24.3 N 5%45% 50% #44 Ni/Cr  38.46 411 3.15E−03 200 0 DC Ar 80%  10% 10% #45Ni/Cr  38.30 412 2.79E−03 200 0 C Ar 70%  20% 10% #55 Si/Al* 44.68 3083.40E−03 200 268.1 27.1 N 5% 45% 50% #61 Si/Al* 44.72 299 3.98E−03 202268.3 27.2 N 5% 45% 50% EXAMPLE #8 #42 Si/Al* 11.0 192 2.11E−03 200 71.424.3 N 5% 45% 50% #44 Ni/Cr  38.46 411 3.15E−03 200 36.5 DC Ar 80%  10%10% #45 Ni/Cr  38.30 412 2.79E−03 200 36.4 DC Ar 70%  20% 10% #55 Si/Al*44.68 308 3.40E−03 200 312.8 27.1 N 5% 45% 50% #61 Si/Al* 44.72 2993.98E−03 202 313.0 27.2 N 5% 45% 50% EXAMPLE #9 #42 Si/Al* 11.0 1922.11E−03 200 71.4 24.3 N 5% 45% 50% #44 Ni/Cr  38.46 411 3.15E−03 20036.5 DC Ar 80%  10% 10% #45 Ni/Cr  38.30 412 2.79E−03 200 36.4 DC Ar70%  20% 10% #55 Si/Al* 44.68 308 3.40E−03 200 223.4 27.1 N 5% 45% 50%#61 Si/Al* 44.72 299 3.98E−03 202 223.6 27.2 N 5% 45% 50% EXAMPLE #10#42 Si/Al* 11.0 192 2.11E−03 200 71.4 24.3 N 5% 45% 50% #44 Ni/Cr  38.46411 3.15E−03 200 36.5 DC Ar 80%  10% 10% #45 Ni/Cr  38.30 412 2.79E−03200 36.4 DC Ar 70%  20% 10% #55 Si/Al* 44.68 308 3.40E−03 200 178.7 27.1N 5% 45% 50% #61 Si/Al* 44.72 299 3.98E−03 202 178.9 27.2 N 5% 45% 50%

As can be seen above, Examples 1-6 and 8-10 were all deposited onrespective glass substrates in a manner so that layer 15 (i.e., theNiCrN_(x)) layer was nitrided as deposited (due to intentionalintroduction of N gas into the sputter chamber including cathode(s) #s44 and 45). However, in comparative Example 7 layer 15 (NiCr) was notnitrided, in order to illustrate the benefits of nitriding layer 15according to this invention. Examples 1-6 and 8-10 illustrate that layer15 can be nitrided (via cathodes/targets 44-45) to various degrees(i.e., the nitrogen (N) flow ranged from 31 sccm in Example 6 up toabout 230 sccm in Example 4). It will be shown below that each of thesehad better characteristics with regard to color stability upon HT thancomparative Example 7 where no nitriding was done to the NiCr layer.Generally, the more nitriding of layer 15, the lower the ΔE value andthus the better the color stability upon HT. Moreover, it can be seenthat Examples 9-10 each had a Si-rich overcoat silicon nitride layerrelative to the other Examples. Examples 8-10 show the effect of N gasflow (mL/kW) on coating stability; e.g., the higher the N gas flow, theless Ni migration and more color stability with HT. While Si-richovercoat silicon nitride layers 17 are appropriate according to certainembodiments of this invention, it will be shown below that the Si-richnature of the overcoat 17 tends to cause sheet resistance (R_(s)) toincrease upon HT which is sometimes not desirable. Thus, it can be seenthat by increasing N gas flow for layer 15, Ni diffusion/migration intothe upper silicon nitride layer can be reduced and/or prevented in orderto provide a coating with more color stability upon HT.

After being sputtered onto glass substrates as set forth above, Examples1-10 were tested and were found to have the following characteristicsmonolithically (not in an IG unit), where the heat treatment (HT)involved heating the respective monolithic products at about 625 degreesC. for about 10 minutes. It is noted that a* and b* color coordinatevalues are in accordance with CIE LAB 1976, Ill. C 2 degree observertechnique, Δa* and Δb* are in terms of absolute value. Moreover, sheetresistance (R_(s)) is in units of ohms per square as is known in theart.

TABLE 5 Characteristics of Examples 1-10 (Monolithic: Before/After HT)EXAMPLES 1-2 Ex. 1 Ex. 1 Ex. 2 Ex. 2 Value/Measurement (pre-HT)(post-HT) (pre-HT) (post-HT) Transmission (TY) %: 9.83 10.57 10.58 11.13L*_(T): 37.54 38.85 38.87 39.79 a*_(T): −0.42 −0.69 −0.59 −0.66 b*_(T):−7.04 −3.81 −6.72 −4.35 Δa*_(T) (transmissive): 0.27 0.07 ΔE*_(T)(transmissive): 3.5 2.5 Glass side 40.29 36.45 39.62 35.66 Reflectance(R_(G)Y %): L*_(G): 69.68 66.86 69.19 66.26 a*_(G): −1.71 −1.80 −1.68−1.72 b*_(G): 2.26 1.88 1.84 1.61 Δa*_(G) (glass side): 0.09 0.04ΔE*_(G) (glass side): 2.8 2.9 Δb*_(G): 0.38 0.23 Film side 35.13 35.0232.77 34.61 Reflectance (R_(F)Y %): L*_(F): 65.85 65.76 63.98 65.44a*_(F): 0.05 0.04 0.32 −0.01 b*_(F): 20.91 15.31 22.32 16.28 R_(s)(ohms/sq.): n/a n/a n/a n/a EXAMPLES 3-4 Ex. 3 Ex. 3 Ex. 4 Ex. 4Value/Measurement (pre-HT) (post-HT) (pre-HT) (post-HT) Transmission(TY) %: 10.66 11.26 10.58 11.42 L*_(T): 39.0 40.01 n/a n/a a*_(T): −0.7−0.69 n/a n/a b*_(T): −6.07 −4.78 n/a n/a Δa*_(T) (transmissive): 0.01n/a ΔE*_(T) (transmissive): 1.6 n/a Glass side 39.3 35.33 38.69 35.71Reflectance (R_(G)Y %): L*_(G): 68.97 66.0 68.52 66.29 a*_(G): −1.71−1.64 −1.68 −1.58 b*_(G): 1.72 1.47 1.74 1.47 Δa*_(G) (glass side): 0.070.10 ΔE*_(G) (glass side): 3.0 2.2 Δb*_(G) (glass side): 0.25 0.27 Filmside 32.71 34.29 33.73 33.92 Reflectance (R_(F)Y %): L*_(F): 63.93 65.1964.75 64.9 a*_(F): 0.3 −0.03 0.15 0.03 b*_(F): 21.58 17.58 19.93 17.86R_(s) (ohms/sq.): n/a n/a n/a n/a EXAMPLES 5-6 Ex. 5 Ex. 5 Ex. 6 Ex. 6Value/Measurement (pre-HT) (post-HT) (pre-HT) (post-HT) Transmission(TY) %: 10.48 11.54 9.5 10.68 L*_(T): 38.69 40.48 n/a 39.03 a*_(T):−0.45 −0.96 n/a −1.32 b*_(T): −7.78 −3.61 n/a −3.63 Δa*_(T)(transmissive): 0.51 n/a ΔE*_(T) (transmissive): 4.6 n/a Glass side39.58 35.39 40.8 36.29 Reflectance (R_(G)Y %): L*_(G): 69.17 66.05 70.066.74 a*_(G): −1.93 −1.98 −2.0 −1.8 b*_(G): 1.46 0.72 1.9 1.15 Δa*_(G)(glass side): 0.05 0.20 ΔE*_(G) (glass side): 3.2 3.4 Δb*_(G) (glassside): 0.74 0.75 Film side 33.39 32.32 35.3 33.4 Reflectance (R_(F)Y %):L*_(F): 64.47 63.61 66 64.48 a*_(F): 0.07 0.24 −0.1 0.52 b*_(F): 22.2315.26 21.6 14.96 R_(s) (ohms/sq.): 41.4 36.0 40.4 39.5 EXAMPLES 7-8 (Ex.7 provided for purposes of comparison to other examples) Ex. 7 Ex. 7 Ex.8 Ex. 8 Value/Measurement (pre-HT) (post-HT) (pre-HT) (post-HT)Transmission (TY) %: 8.02 9.71 9.87 11.37 L*_(T): 34.02 37.32 37.61 40.2a*_(T): 0.03 −1.5 −0.28 −0.92 b*_(T): −8.21 −3.52 −7.61 −3.14 Δa*_(T)(transmissive): 1.53 0.64 ΔE*_(T) (transmissive): 5.9 5.2 Glass side43.58 38.41 40.19 35.52 Reflectance (R_(G)Y %): L*_(G): n/a 71.94 69.6166.15 a*_(G): n/a −2.06 −1.89 −1.91 b*_(G): n/a 2.18 1.85 0.8 Δa*_(G)(glass side): n/a 0.02 ΔE*_(G) (glass side): n/a 3.6 Δb*_(G) (glassside): n/a 1.05 Film side 38 30.1 35.72 33.22 Reflectance (R_(F)Y %):L*_(F): 68.02 61.74 66.31 64.34 a*_(F): −0.32 1.12 −0.15 0.21 b*_(F):21.0 18.65 20.13 13.68 R_(s) (ohms/sq.): 38.8 41.9 41.4 34.5 EXAMPLES9-10 Ex. 9 Ex. 9 Ex. 10 Ex. 10 Value/Measurement (pre-HT) (post-HT)(pre-HT) (post-HT) Transmission (TY) %: 9.74 11.05 9.41 10.08 L*_(T):37.36 39.67 36.76 37.98 a*_(T): −0.25 −1.2 −0.42 −1.52 b*_(T): −7.9−3.78 −7.29 −3.2 Δa*_(T) (transmissive): 0.95 1.10 ΔE*_(T)(transmissive): 4.8 4.4 Glass side 40.34 35.69 40.2 35.35 Reflectance(R_(G)Y %): L*_(G): 69.71 66.29 69.61 66.02 a*_(G): −1.86 −1.63 −1.79−1.33 b*_(G): 1.89 0.99 1.76 1.61 Δa*_(G) (glass side): 0.23 0.46ΔE*_(G) (glass side): 3.5 3.6 Δb*_(G) (glass side): 0.90 0.15 Film side35.91 33.57 37.27 37.22 Reflectance (R_(F)Y %): L*_(F): 66.45 64.6267.48 67.44 a*_(F): −0.21 0.41 −0.54 0.6 b*_(F): 20.6 15.14 20.61 11.42R_(s) (ohms/sq.): 40.7 39.8 41 47

As can be seen from the above, each of Examples 1-6 and 8-10 had goodmatchability (i.e., transmissive and/or glass side reflective ΔE* nogreater than 5.0) because layer 15 was nitrided. However, in Example 7where layer 15 was not nitrided, bad matchability and thus significantcolor shift with HT resulted (i.e., ΔE_(T) was very high in Ex. 7 at5.9). For the other Examples where nitriding of layer 15 was done, ΔE*was no greater than 5.0, more preferably no greater than 4.0 and incertain most preferred instances no greater than 3.0. Meanwhile, it canalso be seen that Example 7 experienced a very high Δa* value of 1.53.In contrast, in the other Examples where nitriding of layer 15 wasconducted according to this invention the Δa* values were much lowerthereby illustrating significantly more color stability upon HT.Accordingly, it can clearly be seen that nitriding of layer 15 accordingto certain embodiments of this invention enables the resulting coatedarticle to have much improved color stability upon lengthy HT (e.g., HTof at least 5 minutes).

For purposes of illustrating how certain color stability numbers werecalculated above, consider Example 3 which had the followingtransmissive values:

L* (before HT): 39.0; L* (after HT): 40.01; ΔL* = 1.01 a* (before HT):−0.70; a* (after HT): −0.69 Δa* = 0.01 b* (before HT): −6.07; b* (afterHT): −4.78 Δb* = 1.29

Thus, using the equation ΔE*=[(ΔL*)²+(Δa*)²+(Δb*)²]^(1/2), (i.e.,equation (1) above), it can be determined that[(1.01)²+(0.01)²+(1.29)²]^(1/2)=(2.6843)^(1/2)=1.6=ΔE*_(T). Thisrelatively low transmissive ΔE* value indicates good matchability(before versus after heat treatment), and is much better (i.e., muchlower) than the 5.9 value for Example 7.

FIGS. 3-4 are XPS plots of Example 1, before and after HT, respectively.In a similar manner, FIGS. 5-6 are XPS plots of Example 2 before andafter HT, respectively; FIGS. 7-8 are XPS plots of Example 3 before andafter HT, respectively; FIGS. 9-10 are XPS plots of Example 4 before andafter HT, respectively; FIGS. 11-12 are XPS plots of Example 5 beforeand after HT, respectively; FIGS. 13-14 are XPS plots of Example 6before and after HT, respectively; FIGS. 15-16 are XPS plots of Example7 before and after HT, respectively; FIGS. 17-18 are XPS plots ofExample 8 before and after HT, respectively; FIGS. 19-20 are XPS plotsof Example 9 before and after HT, respectively; and FIGS. 21-22 are XPSplots of Example 10 before and after HT, respectively. As will beappreciated by those skilled in the art, the nitrogen (N) signalsreported in these Figures are taken from the 1s orbital of N as shown,and so forth. It is noted that the interface of the coating system withthe underlying glass substrate can be seen in these Figs. where Ca andNa begin to rise (e.g., around 750 Å in FIGS. 3-4).

By comparing FIGS. 15-16 (comparative Example 7) with the XPS plots forother examples, it can be seen that when layer 15 is significantlynitrided there is significantly less migration of nitrogen (N) from theupper silicon nitride layer into the NiCr inclusive layer upon HT (ascompared to FIG. 16). This is illustrated, for example, by the fact thatthe N slope 7 a on the lower side of layer 17 is much more steep inFIGS. 4, 6, 8, 10, 12, 14, 18 and 20 (after HT) than in FIG. 16.Moreover, it can be seen in these same Figures that the Ni slope 3 a atthe upper side of layer 15 is much more steep in FIGS. 4, 6, 8, 10, 12,14, 18 and 20 than in FIG. 16; thereby indicating that according tocertain embodiments of this invention there is much less Ni migrationout of layer 15 upon lengthy HT as compared to Example 7. Reduction insuch migrations enables ΔE values to be reduced, thereby permittingbetter color stability upon lengthy HT according to this invention.

In Table 5 above, it can also be seen that in comparative Example 7 thesheet resistance (R_(s)) increased upon HT (this is not desirable incertain instances). This increase in sheet resistance in Example 7 isbelieved to at least partially result from the Ni migrating from layer15 into layer 17 upon HT as shown in FIG. 16. Thus, another surprisingadvantage associated with certain example embodiments of this inventionis that sheet resistance decreases upon HT (e.g., see Examples 5, 6, 8and 9 above). This can be explained by at least the fact that the Nislope 3 a is much more steep at the upper side of layer 15 in FIGS. 4,6, 8, 10, 12, 14, 18 and 20 than in FIG. 16. However, it is noted thatwhile layer 17 may be a Si-rich form of silicon nitride in certainembodiments of this invention, this may cause significant Ni migrationthereby causing sheet resistance to rise upon HT as shown in Example 10(note the less steep Ni slope 3 a in FIG. 22, and the increase in R_(s)upon HT in Table 5). Thus, increasing nitrogen (N) gas flow proximatethe cathode target(s) which form the upper silicon nitride layer enablesproduction of a coated glass article which will more likely experience adecrease in sheet resistance upon HT.

In certain embodiments of this invention, coated articles have a sheetresistance (R_(s)) of no greater than 500 ohms/sq. after HT, morepreferably no greater than 250 ohms/sq. after HT, even more preferablyno greater than about 100 ohms/sq., and most preferably no greater thanabout 41 ohms/sq. after HT. Moreover, in certain preferred embodimentsof this invention, coated articles herein experience a reduction insheet resistance upon HT (in contrast to Example 7). Coated articlesherein in certain example embodiments also have a hemisphericalemissivity (E_(h)) of no greater than about 1.0, more preferably nogreater than about 0.5, and most preferably no greater than about 0.4before and/or after HT.

Another surprising result of certain example embodiments of thisinvention is that nitriding layer 15 results in a more mechanicallydurable (e.g., scratch resistant) coated article after HT. This isbelieved to be because or the chrome nitride present in layer 15. Coatedarticles of certain embodiments of this invention are both chemicallyand mechanically durable. Additionally, monolithic coated articlesaccording to certain embodiments of this invention preferably have avisible transmittance (TY %) of from 5-80% (more preferably from 7-20%)before and/or after HT. Additionally, monolithic coated articlesaccording to certain embodiments of this invention preferably have aglass side reflectance value (R_(G)Y %) of at least 15%, and morepreferably from 20-42% before and/or after HT.

The aforesaid characteristics may be measured at a clear float glassnominal substrate thickness of about 6 mm, or any other suitablesubstrate thickness from 1-12 mm. Moreover, it is noted that the unitsof Examples 1-6 and 8-10 may ultimately be utilized in the context of anIG unit, a vehicle window, or the like.

Certain terms are prevalently used in the glass coating art,particularly when defining the properties and solar managementcharacteristics of coated glass. Such terms are used herein inaccordance with their well known meaning. For example, as used herein:

Intensity of reflected visible wavelength light, i.e. “reflectance” isdefined by its percentage and is reported as R_(x)Y (i.e. the Y valuecited below in ASTM E-308-85), wherein “X” is either “G” for glass sideor “F” for film side. “Glass side” (e.g. “G”) means, as viewed from theside of the glass substrate opposite that on which the coating resides,while “film side” (i.e. “F”) means, as viewed from the side of the glasssubstrate on which the coating resides.

Color characteristics are measured and reported herein using the CIE LABa*, b* coordinates and scale (i.e. the CIE a*b* diagram, Ill. CIE-C, 2degree observer). Other similar coordinates may be equivalently usedsuch as by the subscript “h” to signify the conventional use of theHunter Lab Scale, or Ill. CIE-C, 10⁰ observer, or the CIE LUV u*v*coordinates. These scales are defined herein according to ASTM D-2244-93“Standard Test Method for Calculation of Color Differences FromInstrumentally Measured Color Coordinates” Sep. 15, 1993 as augmented byASTM E-308-85, Annual Book of ASTM Standards, Vol. 06.01 “StandardMethod for Computing the Colors of Objects by 10 Using the CIE System”and/or as reported in IES LIGHTING HANDBOOK 1981 Reference Volume.

The terms “emittance” and “transmittance” are well understood in the artand are used herein according to their well known meaning. Thus, forexample, the term “transmittance” means solar transmittance, which ismade up of visible light transmittance (TY), infrared radiationtransmittance, and ultraviolet radiation transmittance. Total solarenergy transmittance (TS) is then usually characterized as a weightedaverage of these other values. With respect to these transmittances,visible transmittance (TY), as reported herein, is characterized by thestandard CIE Illuminant C, 2 degree observer, technique at 380-720 nm;near-infrared is 720-2500 nm; ultraviolet is 300-800 nm; and total solaris 300-2500 nm. For purposes of emittance, however, a particularinfrared range (i.e. 2,500-40,000 nm) is employed.

Visible transmittance can be measured using known, conventionaltechniques. For example, by using a spectrophotometer, such as a PerkinElmer Lambda 900 or Hitachi U4001, a spectral curve of transmission isobtained. Visible transmission is then calculated using the aforesaidASTM 308/2244-93 methodology. A lesser number of wavelength points maybe employed than prescribed, if desired. Another technique for measuringvisible transmittance is to employ a spectrometer such as a commerciallyavailable Spectrogard spectrophotometer manufactured by PacificScientific Corporation. This device measures and reports visibletransmittance directly. As reported and measured herein, visibletransmittance (i.e. the Y value in the CIE tristimulus system, ASTME-308-85) uses the Ill. C., 2 degree observer.

“Emittance” (E) is a measure, or characteristic of both absorption andreflectance of light at given wavelengths. When transmittance is zero,which is approximately the case for float glass with wavelengths longerthan 2500 nm, the emittance may be represented by the formula:

E=1−Reflectance _(film)

For architectural purposes, emittance values become quite important inthe so-called “mid-range”, sometimes also called the “far range” of theinfrared spectrum, i.e. about 2,500-40,000 nm, for example, as specifiedby the WINDOW 4.1 program, LBL-35298 (1994) by Lawrence BerkeleyLaboratories, as referenced below. The term “emittance” as used herein,is thus used to refer to emittance values measured in this infraredrange as specified by ASTM Standard E 1585-93 for measuring infraredenergy to calculate emittance, entitled “Standard Test Method forMeasuring and Calculating Emittance of Architectural Flat Glass ProductsUsing Radiometric Measurements”. This Standard, and its provisions, areincorporated herein by reference. In this Standard, emittance isreported as hemispherical emittance (E_(h)) and normal emittance(E_(n)). The actual accumulation of data for measurement of suchemittance values is conventional and may be done by using, for example,a Beckman Model 4260 spectrophotometer with “VW” attachment (BeckmanScientific Inst. Corp.). This spectrophotometer measures reflectanceversus wavelength, and from this, emittance is calculated using theaforesaid ASTM E 1585-93 which has been incorporated herein byreference.

Another term employed herein is “sheet resistance”. Sheet resistance(R_(s)) is a well known term in the art and is used herein in accordancewith its well known meaning. It is here reported in ohms per squareunits. Generally speaking, this term refers to the resistance in ohmsfor any square of a layer system on a glass substrate to an electriccurrent passed through the layer system. Sheet resistance is anindication of how well the layer or layer system is reflecting infraredenergy, and is thus often used along with emittance as a measure of thischaracteristic. “Sheet resistance” may for example be convenientlymeasured by using a 4-point probe ohmmeter, such as a dispensable4-point resistivity probe with a Magnetron Instruments Corp. head, ModelM-800 produced by Signatone Corp. of Santa Clara, Calif.

“Chemical durability” or “chemically durable” is used hereinsynonymously with the term of art “chemically resistant” or “chemicalstability”. Chemical durability is determined by boiling a 2″×5″ sampleof a coated glass substrate in about 500 cc of 5% HCl for one hour (i.e.at about 220° F.). The sample is deemed to pass this test (and thus thelayer system is “chemically resistant” or is deemed to be “chemicallydurable” or to have “chemical durability”) if the sample's layer systemshows no visible discoloration or visible peeling, and no pinholesgreater than about 0.003″ in diameter after this one hour boil.

“Mechanical durabilility” as used herein is defined by the followingtests. The test uses a Pacific Scientific Abrasion Tester (orequivalent) wherein a 2″×4″×1″ nylon brush is cyclically passed over thelayer system in 500 cycles employing 150 gm of weight, applied to a6″×17″ sample. In this test, if no substantial, noticeable scratchesappear when viewed with the naked eye under visible light, the test isdeemed passed, and the article is said to be “mechanically durable” orto have “mechanical durability”.

The terms “heat treatment” and “heat treating” as used herein meanheating the article to a temperature sufficient to enabling thermaltempering, bending, or heat strengthening of the glass inclusivearticle. This definition includes, for example, heating a coated articleto a temperature of at least about 600 degrees C. for a sufficientperiod to enable tempering.

Once given the above disclosure many other features, modifications andimprovements will become apparent to the skilled artisan. Such otherfeatures, modifications and improvements are therefore considered to bea part of this invention, the scope of which is to be determined by thefollowing claims:

What is claimed is:
 1. A heat treated coated article comprising: a layersystem supported by a glass substrate, the layer system comprising ametal nitride inclusive layer comprising a nitride of Ni and/or Crlocated between at least first and second dielectric layers, wherein thesecond dielectric layer is at least partially nitrided and positioned sothat the metal nitride inclusive layer is between the second dielectricand the glass substrate; and wherein said coated article has atransmissive ΔE*_(T) value no greater than 4.0 after heat treatment. 2.The coated article of claim 1, wherein the coated article has atransmissive ΔE*_(T) value no greater than 3.0 after heat treatment. 3.The coated article of claim 1, wherein the coated article has atransmissive Δa* value no greater than 1.1 after heat treatment.
 4. Thecoated article of claim 1, wherein the coated article has a transmissiveΔa* value no greater than 0.8 following heat treatment.
 5. The coatedarticle of claim 1, wherein each of said first and second dielectriclayers comprise silicon nitride.
 6. The coated article of claim 1,wherein each of said first and second dielectric layers are nitrided,and wherein said metal nitride inclusive layer contacts each of saidfirst and second dielectric layers.
 7. The coated article of claim 1,wherein said metal nitride inclusive layer comprises a nitride of Cr. 8.A heat treated coated article comprising: a layer system supported by aglass substrate, said layer system comprising a metal nitride inclusivelayer located between at least first and second dielectric layers,wherein the second dielectric layer is at least partially nitrided andpositioned so that the metal nitride inclusive layer is between thesecond dielectric layer and the glass substrate; and wherein said coatedarticle has a glass side reflective ΔE*_(G) value no greater than 4.0after heat treatment.
 9. The coated article of claim 8, wherein saidcoated article has a glass side reflective ΔE*_(G) value no greater than3.0 after heat treatment.
 10. The coated article of claim 8, whereineach of said first and second dielectric layers comprises a nitride, andwherein said metal nitride inclusive layer is in contact with each ofsaid first and second dielectric layers.
 11. The coated article of claim8, wherein said heat treatment comprises heating the coated article forat least about five minutes at a temperature of at least about 600degrees C.
 12. The coated article of claim 1, wherein said heattreatment is for at least about five minutes at a temperature of atleast about 600 degrees C.
 13. A coated article comprising: a layersystem supported by a glass substrate, said layer system comprising ametal nitride inclusive layer comprising a nitride of Ni and/or Crlocated between at least first and second dielectric layers, whereinsaid second dielectric layer is at least partially nitrided andpositioned so that the metal nitride inclusive layer is between thesecond dielectric layer and the glass substrate; and means for enablingthe coated article to have a transmissive ΔE*_(T) value no greater than5.0 if thermally tempered.
 14. The coated article of claim 13, furthercomprising means for enabling the coated article to have a transmissiveΔE*_(T) value no greater than 4.0 if thermally tempered.
 15. The coatedarticle of claim 13, further comprising means for enabling the coatedarticle to have a transmissive ΔE*_(T) value no greater than 3.0 ifthermally tempered.
 16. The coated article of claim 8, wherein the metalnitride inclusive layer comprises a nitride of Ni and/or Cr.